A communication module which is used in radio communication includes, for example, a power amplifier, an impedance matching circuit, and so forth. In this power amplifier, a nonlinear power amplifier is usually used. Since the nonlinear power amplifier uses a rectangular wave signal, the power efficiency thereof is generally higher than the power efficiency of a linear power amplifier using a sinusoidal signal.
On the other hand, an output signal of the nonlinear power amplifier contains many harmonic components. In order to remove these harmonic components, a high-performance external filter is generally used; however, the filter occupies a large space in the communication module.